Decoy flares are used defensively by combat aircraft to evade heat-seeking missiles directed at such aircraft by an enemy. At an appropriate time after the enemy launches a heat-seeking missile, the targeted aircraft releases a decoy flare. The decoy flare burns in a manner that simulates the engines of the targeted aircraft. Ideally, the missile locks onto and destroys the decoy, permitting the targeted aircraft to escape unharmed.
The burn requirements of the decoy flare are therefore determined by reference to the known characteristics of the targeted aircraft's engine emissions as interpreted by the heat-seeking missile. It is necessary for the decoy to burn at a temperature and for a duration that will induce the missile to lock onto the decoy instead of the escaping friendly aircraft. It may also be necessary for the decoy to emit certain wavelengths while burning, as some missiles examine a potential target's energy spectrum in order to distinguish decoys from targeted aircraft by the presence of wavelength signatures.
A central goal in the decoy flare art is to produce satisfactory decoy flares in an efficient and cost-effective manner. It is generally sufficient for the decoy to cause the missile to lock on to and destroy the decoy. Because a missile destroys each successful decoy, producing decoys that substantially exceed the burn requirements is not an important goal. A decoy that far exceeds the burn requirements will be destroyed just as promptly as one that barely satisfies the burn requirements. The goal of producing effective flares in turn requires efficient and cost-effective production of flare pellets.
Each decoy flare contains a flare pellet which is ignited when the decoy is deployed. The burning flare pellet produces the heat and other emissions needed to satisfy the decoy's burn requirements and thus permit the missile to lock onto the decoy. The flare pellet includes a shaped quantity of flare material which is coated with an ignition composition.
The flare material is shaped by a process which includes consolidation under pressure, followed by milling. In the first step, the flare material is consolidated by being compressed in a mold. Typical flare materials contain synthetic resin polymers such as polytetrafluoroethylene. During consolidation, these synthetic resin polymers tend to flow and form a solid matrix with other components of the flare material.
Conventional flare molds include two die faces which engage one another along an outer edge to form an enclosed space. The enclosed space generally defines a grooved six-sided rectangular solid. The flare material is compressed and consolidated within this enclosed space by pressure from the die faces.
The die faces are shaped to impress grooves into two opposite sides of the consolidated flare material. Grooves may also be impressed by the dies into the ends of the pellet. Grooves increase the surface area of the flare pellet relative to its volume, thereby assisting the pellet in meeting the burn requirements. In some instances, grooves are also impressed into the remaining two sides of the pellet. However, the dies and equipment needed to impress grooves into all six sides of the pellet are often prohibitively complex and expensive.
When grooves are impressed only into two sides of the pellet, the surface area of the pellet is typically insufficient to satisfy the burn requirements, and the addition of grooves by other means is required. Moreover, it has been thought that performance of the pellet may be unsatisfactory unless grooves are placed symmetrically in all four sides of the pellet. Thus, additional grooves are generally cut into the two groove-free sides of the pellet by a milling step after consolidation. After milling, all four sides and both ends of the pellet contain grooves that increase the pellet's surface area. The milled pellet is then coated with an ignition composition and installed in a decoy flare housing.
This milling step is expensive for several reasons. The milling process requires special cutter equipment and a worker to operate the cutters. The cutters require regular maintenance and/or repair. Maintenance and repair are needed to ensure the accuracy of the cut, to permit clean cuts, and to avoid injuries to cutter operators.
Milling also increases the amount of flare material used per pellet. The material removed from a consolidated pellet by milling cannot be reused. The formation of a solid matrix between the flowing synthetic resin polymers and the other flare material components cannot be reformed by subsequent consolidations. Thus, the removed material must be collected and moved to another area for proper disposal. In an existing operation, approximately fifteen percent of every batch of flare mix is cut out by milling instead of being used in pellets. Moreover, the costs of disposing of the milled material in an environmentally acceptable manner are significant.
Thus, it would be an advancement in the art to provide a process for making flare pellets which eliminates the need for milling after consolidation but nonetheless provides pellets that satisfy the predetermined burn requirements.
Such a process and flares are disclosed and claimed herein.